White House press secretary Sean Spicer on Thursday revealed that the Trump administration was considering a 20% tax on all imports from Mexico as a way to pay for the southern border wall.

Spicer didn’t give any additional details, according to a White House pool report, but said it would be the beginning of a process that would be part of overall tax reform. His comments are the first word from the new administration on just how Trump was going to get Mexico, which has repeatedly said it will not pay for the wall, to pony up.

“By doing it that we can do $10 billion a year and easily pay for the wall just through that mechanism alone. That’s really going to provide the funding,” Spicer said. “It clearly provides the funding and does so in a way that the American taxpayer is wholly respected.”

Initially, Spicer told the White House press corps that Trump planned on imposing the tax for the wall, but later walked that back, saying it was one of many options the administration was considering.

"There’s nothing to roll out, so the idea of asking for details on something, we’re not there yet… It could be a multitude of things. Instead of 20% it could be 18, it could be 5,” Spicer said. “The idea is to show that generating revenue for the wall is not as difficult as some might have suggested.”

Of the 1,000 miles of border Trump wants to build the wall on, 350 miles lack a vehicle barrier or fence.

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PolitiFact reported that it could cost from $5.1 billion to $25 billion to finish fencing off the US–Mexico border, plus additional money to maintain it. The cost for a brick-and-mortar wall could balloon up to $40 billion, according to MIT Technology Review.

Mexico was the second-largest supplier to agricultural imports to the US in 2015, totaling $21 billion, according to the Office of the United States Trade Representative. The top categories were fresh vegetables, fruit, and wine and beer.

It was also the US’s third-largest supplier of goods imports in 2015.

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Motorists in line at the US–Mexico border in Tijuana, Mexico, Jan. 25, 2017.

The wall would lift up US workers' wages by stopping the flow of cheap immigrant labor, Spicer said.

The US's current policy, he added, is to tax exports and let imports flow freely in.

“We are probably the only major country that doesn’t treat imports this way,” Spicer said. “This gets us in line frankly with the policies that the other countries around the world treat our products.”

Spicer said the tax plan was something the administration had been in close contact with members of Congress. For months, Republicans in Congress have been looking into a tax proposal that would include imposing new taxes on imports.

Adolfo Flores is a national security correspondent for BuzzFeed News and is based in Los Angeles. He focuses on immigration.